Buggy code:
@ SuppressWarnings ( "unchecked" ) public class QueryResponse extends SolrResponseBase { private NamedList < Object > _header = null ; private SolrDocumentList _results = null ; private NamedList < ArrayList > _sortvalues = null ; private NamedList < Object > _facetInfo = null ; private NamedList < Object > _debugInfo = null ; private NamedList < Object > _highlightingInfo = null ; private NamedList < Object > _spellInfo = null ; private NamedList < Object > _statsInfo = null ; private NamedList < Object > _termsInfo = null ; private Map < String , Integer > _facetQuery = null ; private List < FacetField > _facetFields = null ; private List < FacetField > _limitingFacets = null ; private List < FacetField > _facetDates = null ; private Map < String , Map < String , List < String > > > _highlighting = null ; private SpellCheckResponse _spellResponse = null ; private TermsResponse _termsResponse = null ; private Map < String , FieldStatsInfo > _fieldStatsInfo = null ; private Map < String , Object > _debugMap = null ; private Map < String , String > _explainMap = null ; private transient final SolrServer solrServer ; public QueryResponse ( ) { } public QueryResponse ( NamedList < Object > res , SolrServer solrServer ) { } @ Override public void setResponse ( NamedList < Object > res ) { } private void extractSpellCheckInfo ( NamedList < Object > spellInfo ) { } private void extractTermsInfo ( NamedList < Object > termsInfo ) { } private void extractStatsInfo ( NamedList < Object > info ) { } private void extractDebugInfo ( NamedList < Object > debug ) { } private void extractHighlightingInfo ( NamedList < Object > info ) { } private void extractFacetInfo ( NamedList < Object > info ) { <START_BUG> _facetQuery = new HashMap < String , Integer > ( ) ; <END_BUG> NamedList < Integer > fq = ( ( NamedList < Integer > ) ( info . get ( "facet_queries" ) ) ) ; if ( fq != null ) { for ( Map . Entry < String , Integer > entry : fq ) { _facetQuery . put ( entry . getKey ( ) , entry . getValue ( ) ) ; } } NamedList < NamedList < Number > > ff = ( ( NamedList < NamedList < Number > > ) ( info . get ( "facet_fields" ) ) ) ; if ( ff != null ) { _facetFields = new ArrayList < FacetField > ( ff . size ( ) ) ; _limitingFacets = new ArrayList < FacetField > ( ff . size ( ) ) ; long minsize = _results . getNumFound ( ) ; for ( Map . Entry < String , NamedList < Number > > facet : ff ) { FacetField f = new FacetField ( facet . getKey ( ) ) ; for ( Map . Entry < String , Number > entry : facet . getValue ( ) ) { f . add ( entry . getKey ( ) , entry . getValue ( ) . longValue ( ) ) ; } _facetFields . add ( f ) ; FacetField nl = f . getLimitingFields ( minsize ) ; if ( ( nl . getValueCount ( ) ) > 0 ) { _limitingFacets . add ( nl ) ; } } } NamedList < NamedList < Object > > df = ( ( NamedList < NamedList < Object > > ) ( info . get ( "facet_dates" ) ) ) ; if ( df != null ) { _facetDates = new ArrayList < FacetField > ( df . size ( ) ) ; for ( Map . Entry < String , NamedList < Object > > facet : df ) { NamedList < Object > values = facet . getValue ( ) ; String gap = ( ( String ) ( values . get ( "gap" ) ) ) ; Date end = ( ( Date ) ( values . get ( "end" ) ) ) ; FacetField f = new FacetField ( facet . getKey ( ) , gap , end ) ; for ( Map . Entry < String , Object > entry : values ) { try { f . add ( entry . getKey ( ) , Long . parseLong ( entry . getValue ( ) . toString ( ) ) ) ; } catch ( NumberFormatException e ) { } } _facetDates . add ( f ) ; } } } public void removeFacets ( ) { } public NamedList < Object > getHeader ( ) { } public SolrDocumentList getResults ( ) { } public NamedList < ArrayList > getSortValues ( ) { } public Map < String , Object > getDebugMap ( ) { } public Map < String , String > getExplainMap ( ) { } public Map < String , Integer > getFacetQuery ( ) { } public Map < String , Map < String , List < String > > > getHighlighting ( ) { } public SpellCheckResponse getSpellCheckResponse ( ) { } public TermsResponse getTermsResponse ( ) { } public List < FacetField > getFacetFields ( ) { } public List < FacetField > getFacetDates ( ) { } public FacetField getFacetField ( String name ) { } public FacetField getFacetDate ( String name ) { } public List < FacetField > getLimitingFacets ( ) { } public < T > List < T > getBeans ( Class < T > type ) { } public Map < String , FieldStatsInfo > getFieldStatsInfo ( ) { } }

Fix:
_facetQuery = new LinkedHashMap < String , Integer > ( ) ;